public MainWindow()
        {
            InitializeComponent();

            VM = new ViewModel();

            CommandBindings.Add(VM.SaveCommandBinding);
            CommandBindings.Add(VM.ToggleItemSelectionCommandBinding);

            R.AddHandler(
                FrameworkElement.MouseDownEvent,
                new RoutedEventHandler((a, b) =>
            {
                var part = b.OriginalSource as Border;
                if (part != null)
                {
                    VM.ToggleItemSelectionCommandBinding.Command.Execute(part.DataContext);
                }
            }));

            R1.AddHandler(
                FrameworkElement.MouseDownEvent,
                new RoutedEventHandler((a, b) =>
            {
                var part = b.OriginalSource as Border;
                if (part != null)
                {
                    VM.ToggleItemSelectionCommandBinding.Command.Execute(part.DataContext);
                }
            }));
        }